Fix REAME.md typos in installation script

Author: xinye1

README.md

@@ -16,7 +16,7 @@ Fcitx5 theme based on Nord color.
 git clone https://github.com/tonyfettes/fcitx5-nord.git
 mkdir -p ~/.local/share/fcitx5/themes/
 cd fcitx5-nord
-cp -r nord-dark/ nord-light/ ~/.local/share/fcitx5/themes/
+cp -r Nord-Dark/ Nord-Light/ ~/.local/share/fcitx5/themes/
 ```
 
 ### Enabling